About an hour’s drive from where this is being written there is a car plant, and as you drive past its entrance you may notice an unobtrusive sign and an extra lane with the cryptic road marking “H2”. The factory is the Honda plant at Swindon, it produces some of Europe’s supply of Civics, and the lane on the road leads to one of the UK or indeed the world’s very few public hydrogen filling stations. Honda are one of a select group of manufacturers who have placed a bet on a future for environmentally sustainable motoring that lies with hydrogen fuel cell technologies.
The trouble for Honda and the others is that if you have seen a Honda Clarity FCV or indeed any hydrogen powered car on the road anywhere in the world then you are among a relatively small group of people. Without a comprehensive network of hydrogen filling stations such as the one in Swindon there is little incentive to buy a hydrogen car, and of course without the cars on the road there is little incentive for the fuel companies to invest in hydrogen generating infrastructure such as the ITM Power electrolysis units that seem to drive so many of the existing installations. By comparison an electric car is a much safer bet; while the charging point network doesn’t rival the gasoline filling station network there are enough to service the electric motorist and a slow charge can be found from most domestic supplies.
A pipeline to deliver a pipe dream?
The hydrogen economy then has been something of a pipe dream for environmentalists, holding the promise of pollution-free energy but with barriers too steep for its likely adoption. It was welcome then that our attention was recently drawn via an Ars Technica article to a plan for a pilot hydrogen distribution scheme resulting from a tie-up between British and Norwegian domestic gas companies. They are suggesting the complete conversion from methane to hydrogen of the domestic natural gas distribution network covering a substantial part of Northern England, with the hydrogen being derived from catalytic reforming and the resulting carbon dioxide being sequestered in depleted oil and gas fields beneath the North Sea. It’s being sold as a blueprint for the decarbonisation of the natural gas industry, and while it still relies on a fossil feedstock rather than the environmentalist’s dream of sustainable electrolysis of seawater, it holds the promise of minmum atmospheric CO2 release that other projects such as the hydrogen-blending HyDeploy do not.
The report delves deeply into the economics of the project, but this is Hackaday. We’re more interested in the technology involved, and in what this development might mean for the future. And to fully understand it all, we first have to take a quick detour into the gas industry’s past.
When we think about domestic gas, it is almost certainly methane, so-called natural gas from underground fossil deposits. We have become used to its blue flame through countless TV adverts showing us clean and high-tech new boilers, cozy homes and mouthwatering food delivered from sparkling new cookers, but it’s not the gas our grandparents would have known. Their gas came from coal, and each and every town would have had a gas works, in effect a small chemical works in its own right, producing it locally without access to any national or regional grids. The gas itself was a mixture mostly composed of carbon monoxide and hydrogen, and with a succession of purification steps was manufactured from coal by alternately heating it in a limited supply of air to produce carbon monoxide, then blasting it with high-pressure steam to produce hydrogen. It seemed the Older Generation had no end of tales of sooty and temperamental gas appliances, and the gas works themselves were notoriously dirty and polluted environments whose former sites are often still contaminated to this day.
In the later half of the 20th century with the arrival of plentiful supplies of methane natural gas, the industry was converted to this new source. New distribution grids were installed, and a huge operation was mounted in which engineers visited every gas customer to convert their appliances with new jets or burners to suit the different combustion properties of the new supply. For most of the UK for example this process was completed during the 1960s and 1970s, and it is into part of the resulting network and appliances that hydrogen is proposed to replace the methane.
Brittle cookers and not-so-brittle pipes
On the face of it then, the conversion of the network from methane to hydrogen should resemble that exercise from five decades ago. In fact it should even be simpler, because the gas grid that needed to be build for the switch to methane is already in place. But there’s a problem, and it stems from one of the unusual properties of hydrogen. A hydrogen molecule is tiny in the scheme of such things, and readily inserts itself into the crystal lattice of most metals. In some cases this is a desired property, for example there has been significant research into the possibility of storing hydrogen in this way in metallic palladium, but in the context of gas pipes or fittings there is a potential for disaster.
In forming what is in effect an alloy of the metal and hydrogen, the properties of the metal are radically changed; the phenomenon is referred to as hydrogen embrittlement. Low-pressure local gas mains in the UK are a distinctive yellow polypropylenethat is immune to embrittlement and strong enough that it has been used as fighting robot armour, but long-distance high-pressure pipelines are metal. If the metal of a high-pressure gas main is embrittled in this way the results could be catastrophic, and if for example it happened to the metal parts of domestic cooking stoves designed for use with methane it could be responsible for gas leaks. The pilot scheme’s document goes into detail on the selection of carbon steel as the most suitable pipeline material, but is surprisingly light on the same topic for whatever metal fittings may be found at the user end.
The proposal is a fascinating read for anyone with an interest in green energy and in hydrogen as an energy source in particular. As a decarbonisation solution to a natural gas network it is certainly bold, outlining the kind of project that should it go ahead will be cited by journal articles and historians in a century’s time, and as an introduction to hydrogen energy schemes for the uninformed it is certainly comprehensive.
Returning to the start of this article and those hydrogen cars, will it deliver hydrogen-powered motoring? It’s certainly true that a ready source of hydogen would make establishing a filling station network a much easier task, but while we admit that this may be one of those prophecies that doesn’t stand the test of time, we can’t quite see it. The early promise that existing internal combustion engined cars would readily convert to hydrogen has proved over-optimistic, fuel cell cars such as the Honda are expensive and early in their development, and meanwhile the uptake of electric cars appears to have leapfrogged both technologies. As you might expect, we want to believe, but it’s a significantly greater likelihood that we’ll be traveling to the hacker camps of the 2030s by electric rather than hydrogen power. That our homes will be heated using the new fuel by then though seems to be a distinct possibility.
Header image: Bexim [CC BY-SA 4.0].